Diagnostic testing is expanding from centralized hospital labs to more distributed settings in both the developed and developing worlds. A current dominant point-of-care diagnostic test format is the lateral flow immunoassay (LFIA), which relies on capillary wicking of fluids through porous nitrocellulose strips. Such tests typically rely on the specific binding between gold-labeled biomarkers with capture antibodies immobilized at the test line of the solid phase. Current devices possess many desirable features, such as being rapid, inexpensive, portable, and easy to use. However, these devices suffer from a limitation in sensitivity related to the small sample volume that limits the biomarker repertoire to those at relatively higher blood and plasma concentrations. These limitations have created a need for rapid and simple sample processing strategies for purifying and enriching biomarkers in a form that could then be applied directly to the existing lateral flow tests or other types of newly developed rapid tests.
The lateral flow or “dipstick” immunochromatographic assay represents a current dominant point-of-care technology capable of rapidly detecting protein biomarkers in bodily fluids (e.g., blood, urine) that is compatible with the constraints of low resource settings, such as lack of electricity and optical instrumentation. These advantages have led to widespread acceptance and consolidation within the marketplace of “dipstick” type products that are profitably manufactured and sold to consumers as rapid diagnostic tests.
However, as noted above, the range of biomarkers that are detectable by immunochromatography is ultimately limited to proteins of relatively high abundance in the plasma in part because of the inability of an immunochromatographic flow strip to process larger volumes of biological sample so as to accumulate sufficient quantities of dilute labeled biomarkers to generate a detectable signal. This deficiency has created a need for simple yet robust biomarker purification/enrichment strategies that can improve test sensitivity while leveraging the success and widespread acceptance of lateral flow rapid diagnostic tests.
Despite the advances in the development of diagnostic testing methods and devices for expanding from centralized hospital labs to more distributed settings, a need a exists for improved diagnostic testing methods and devices that overcome the disadvantages of those presently used. The present invention seeks to fulfill this need and provides further related advantages.